Pickproof cylinder lock

ABSTRACT

A PICKPROOF CYLINDER LOCK HAS A BOLT MOUNTED FOR SLIDING MOVEMENT IN THE CYLINDER AND A PLURALITY OF SPRINGTENSIONED PINS ASSOCIATED WITH THE BOLT AND NORMALLY BLOCKING MOVEMENT OF THE BOLT SO AS TO MAINTAIN THE LATTER IN A LOCKED POSITION. THE PINS ARE MOVED TO A POSITION IN WHICH THEY UNLOCK THE BOLT WHEN THE PROPER KEY IS INSERTED IN THE LOCK. INSERTION OF THE KEY ALSO TENSIONS AN ACTUATING MEMBER WHICH IS REMOTE FROM THE PINS AND RELEASES THE ACTUATING MEMBER WHEN THE KEY REACHES ITS FULLY INSERTED POSITION, THE RELEASED ACTUATING MEMBER THEREUPON IMPARTING A SHARP, INSTANTANEUOUS ACTUATING STROKE TO THE BOLT TO DRIVE IT TO AN UNLOCKED POSITION OF THE BOLT HAS BEEN UNBLOCKED BY THE PINS.

Sept. 20, 1971 N. EPSTElN 3,

PICKPROOF CYLINDER LOCK Filed Oct. 31. 1969 2 Sheets-Sheet 1 INVENTOR.

NORMAN EPZC ATTORNEY Sept. 20, 1971 N. EPSTEIN PICKPROOF CYLINDER LOCK 2 Sheets-Sheet 2 Filed Oct. 31, 1969 irlli lllllif m R E ma D. WE m N A M R O N United States Patent Oflice Patented Sept. 20, 1971 US. Cl. 70-364A 9 Claims ABSTRACT OF THE DISCLOSURE A pickproof cylinder lock has a bolt mounted for sliding movement in the cylinder and a plurality of springtensioned pins associated with the bolt and normally blocking movement of the bolt so as to maintain the latter in a locked position. The pins are moved to a position in which they unblock the bolt when the proper key is inserted in the lock. Insertion of the key also tensions an actuating member which is remote from the pins and releases the actuating member when the key reaches its fully inserted position, the released actuating member thereupon imparting a sharp, instantaneous actuating stroke to the bolt to drive it to an unlocked position if the bolt has been unblocked by the pins.

BACKGROUND OF THE INVENTION The present invention relates to locks of the cylinder type, and in particular to a lock which is pick-proof. The lock requires the use of a special key which is adapted not only to operate the tumbler pins to release a bolt, but to store energy in an actuating member which is released to strike and drive the bolt to a position in which the lock can be opened.

In conventional cylinder locks a plug or cylinder is rotatably mounted in a housing, and the lock is opened by turning the cylinder within the housing after the proper key has been inserted through the keyhole. The cylinder is normally restrained from turning movement by a number of pin tumblers of diiferent lengths and comprising upper and lower segments which are spring biased downwardly into the keyway slot. When the proper key is inserted in the lock, each of the pin tumblers is elevated to a selected position in which the juncture of the upper and lower segments register with the outer circumference of the cylinder. Thus, by turning the inserted key, the cylinder may be rotated, carrying with it the lower pin sections and leaving the upper sections in the lock housing.

In the conventional locks described above, the lock can be readily picked by an experienced person since a torque force can be applied to the cylinder while a picking tool is used to elevate each of the pin tumblers. The torque force applied to the cylinder effects a frictional bearing upon the pin tumblers which can be felt by the person picking the lock. Thus, as the pin tumblers are raised, the person can ascertain by feel a slight movement of the cylinder when the pin reaches its release position.

It is an object of the present invention to provide a cylinder lock in which there is no frictional bearing provided between any of the lock parts during the opening operation so that a person tampering with the lock can feel no movement therein, and thus the lock is pick-proof.

A further object of the invention is the provision of a pick-proof lock of the character described in which the lock mechanism is designed to be operated by a key of special construction which is effective not only to elevate the contained tumblers to their proper release positions, but to withhold final unlocking of the lock until the key tensions an actuating member and releases it to impart an actuating stroke to the slidable bolt, which actuating stroke does not occur until the key reaches its fully-inserted position within the lock.

Another object of the invention is the provision of a lock of the character described in which the actuating member is entirely remote from the pin tumblers and applies no force or pressure thereto, and in which the actuating stroke is instantaneous and temporary, being elfective to drive the bolt to a lock-release position only after the pin tumblers have already been elevated to their proper position.

SUMMARY OF THE INVENTION A pick-proof lock comprises a cylinder rotatably mounted in a housing and having a bolt mounted therein for sliding movement between a locking position and an unlocking position. A plurality of pins are also mounted in the cylinder and associated with the bolt in such a manner as to normally maintain the bolt in its locking position and obstruct movement of said bolt to its unlocking position, the pins being movable, upon insertion of the proper key into the lock, to selected positions in which they release said bolt for movement. An actuating member is also mounted in said cylinder and associated with means operable upon insertion of the proper key into said lock, to tension said actuating member and release the latter when the key reaches its fully-inserted position, the released actuating member imparting an actuating stroke to said bolt in a direction to drive the released bolt to its unlocking position.

Additional objects and advantages of the invention will become apparent during the course of the following specification when taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of an assembled lock made in accordance with the invention;

FIG. 2 is an enlarged central section taken along line 22 of FIG. 1 and showing the lock parts in their locked condition before the insertion of a key therein;

FIG. 3 is a section similar to FIG. 2, but showing the condition of the lock parts with a key partially inserted;

FIG. 4 is a section similar to FIG. 2, but showing the condition of the lock parts with a key fully inserted in the lock;

FIG. 5 is a section taken along line 5-5 of FIG. 2;

FIG. 6 is an exploded perspective view of internal parts of the lock;

FIG. 7 is an enlarged perspective view of the actuating spring of the lock and its associated cam member;

FIG. 8 is an enlarged section taken along line 88 of FIG. 3; and

FIG. 9 is an enlarged section taken along line 99 of FIG. 4.

lReferring in detail to the drawings, there is illustrated a lock incorporating pickproof structure made in accordance with the present invention. As shown in FIG. 1, the lock 10 comprises a hollow cylindrical casing 12 within which is rotatably mounted the lock cylinder 14.

The cylinder 14 has in its front wall the usual keyhole 16 communicating with a longitudinal keyway slot 18 into which a key 20 may be inserted. In contrast to conventional tumbler locks, the keyhole 16 and slot 18 are not centrally located in the cylinder 14. Rather, they are offset from the center, and in the locked position shown in FIG. 2, the keyhole is located adjacent the bottom edge of the cylinder. After the key has been properly inserted, to open the lock, the key is revolved in a circular path, thereby rotating the cylinder. To facilitate this revolving movement of the key, the front surface of the cylinder is formed with a projecting finger piece 22 which may be engaged by the fingers of the hand holding the inserted key so that the hand may provide a twisting motion to rotate the cylinder.

As shown in FIGS. 2 and 6 the circumferential edge portion of cylinder 14, diametrically opposed to the edge portion containing keyhole 16, is cut away to provide a longitudinal groove 24. Through this groove are drilled a row of circular bores 26 extending diametrically through the cylinder 14. In each of the bores 26, a pin 28 is slidably located, the pins being urged through the lower ends of the bores 2.6 by respective coil' springs 30. The lower ends of springs 30 are connected to the respective pins 28, and the upper ends thereof are seated against a plate 32 which overlies and covers over the ends of bores 26.

When no key is inserted in slot 18, the pins 28 are urged downwardly through their respective bores until their free, rounded ends are located at the same level within slot 18, as shown in FIG. 2. It will thus be appreciated that the pins 28 do not operate in the manner of conventional looks, that is to say they do not block the turning movement of the cylinder 14 within the casing 12. Rather, the pins 28, when properly aligned, operate to release a bolt 34 which then couples the cylinder 14 to latch mechanism 36 connected to a door latch or the like.

As shown in FIGS. 2-5, the latch mechanism 36 comprises a flat bar 38 extending through a circular opening 40 in the rear wall 12a of casing 12. The opening 40 communicates with a circular recess 41 in the rear wall 12a, which recess 41 in turn communicates with a circular recess 42 of larger diameter. The opening 40 and recesses 41 and 42 are concentric. The bar 38 has an enlarged end portion 43 having a slot 44 at its center in which one end of a coil spring 45 is seated. The enlarged end portion 43 is rotatably received within the circular recess 41.

A coupling disc 46 is rotatably seated within the large circular recess 42 and is keyed to the enlarged end portion 43 of the bar 38 by means of slot 46a (FIG. 6), so that the bar 38 is turned when the coupling disc 46 is rotated. The coupling disc 46 has a central circular aperture 47 through which the coil spring 45 extends freely. The disc 46 also has a circular aperture 48 offset from its center and sized and positioned to receive the end of bolt 34, in a manner to be presently explained.

The latch mechanism 36 also comprises a flat plate 49 having a pair of spaced pins 50 and 51 which project perpendicularly from the front surface thereof and extend slidably into corresponding bores 52 and 53 which open through the rear of the cylinder 14, as shown in FIG. 6. As also best seen in the view, the rear portion of the cylinder 14 is cut away to provide a segmented terminal extension 14a having a fiat rear surface. The plate 49 is sized to fit within the recessed portion of the cylinder 14 adjacent to this extension 14a, as shown best in FIG. 5, and when the pins 50 and 51 are fully inserted within bores 52 and 53, the plate 49 rests flush against the rear wall of cylinder 14. The coil spring 45 carried by the bar 38, projects through the central opening 47 in coupling disc 46 and bears against the rear surface of plate 49, biasing said plate 49 against the rear wall cylinder 14, as shown in FIGS. 2 and 5. The bolt 34 is cut away at its rear end to provide a semi-circular rear end portion 34a which is slidably received within a semi-circular aperture 54 formed in plate 49. The end of this bolt rear end portion 34a provides a shoulder which is engaged by the plate 49.

As shown in FIG. 2, the bolt 34 projects rearwardly from the rear wall of cylinder 14 and its end portion 34a extends through the semi-circular aperture 54 in plate 49. The spring 45 biases the plate 49 forwardly against the cylinder rear wall so that the plate 49 is spaced from the coupling disc 46 and the bolt is maintained by plate 49 in an inoperative position in which its end portion 34a is remote from said disc 46. Thus, while the cylinder 14 may be freely rotated, carrying the bolt 34 and plate 49 with it, such rotating movement does not affect the latch mechanism 36, since the disc 46 is uncoupled from the bolt 34, and the latch of the door or the like will not be opened.

A longitudinal bore 56 is drilled through the rear wall of cylinder 14, the bore 56 extending through cylinder 14 and terminating short of the front surface thereof, as shown in FIG. 2. The bolt 34 is cylindrical and is slidably mounted in the bore 56. It will be observed in FIGS. 5 and 6 that the bore 56 is located slightly olf-center of the longitudinal axis of the cylinder 14, and that it communciates with the pin bores 26.

Intermediate its ends, the bolt 34 is formed with a row of arcuate notches 58 which are spaced apart by the same distance as the spacing between the pins 28. In the inoperative position shown in FIG. 2, the spring-biased plate 49 maintains the bolt 34 in such a location within the bore 56 that the notches 58 are precisely aligned with the respective pins 28 and embrace the same, as shown in FIG. 5. The location of the pins 28 within the bolt notches 58 locks the bolt 34 in its inoperative position and prevents longitudinal sliding movement thereof within the bore 56.

Each of the pins 28 is formed with a recessed portion 60 of reduced diameter which is sized to register with the 'bolt 34 so as to provide clearance between the bolt 34 and the pin 28, in the manner shown in FIG. 4. Thus, when the recessed portions 60 of all of the pins are aligned with the bolt 34', the pins 28 no longer fill the notches 58 to block longitudinal movement of the bolt, but rather the registering recessed portions permit the bolt to be moved longitudinally into coupled engagement with the latch mechanism 36 in a manner to be presently explained.

The recessed portions 60 are located at different positions longitudinally along the extent of each of the pins 28, so that in the normal, downwardly-biased positions of the pins 28, shown in FIG. 2, where no key is inserted in the lock, each of the recessed portions 60 are located at a different level, and each is out of registry with bolt 34. When the proper key 20 for lock 10 is fully inserted in slot 18, the slots and ridges on the key will raise the individual pins 28, each to the proper level, so that the recessed portions 60 of all the pins are in alignment with the bolt 34, and the latter is free to move longitudinally. In FIG. 4, the key 20 is shown fully inserted, and all of the recessed portions 60 of pins 28 are in alignment with bolt 34, these recessed portions being directly behind bolt 34, as viewed in FIG. 4. It will *be appreciated that each of the pins 28 must be raised by the key to exactly the correct level in which its recessed portion 60 is in registry with bolt 34, and thus if any one of the pins is at the incorrect level (as by use of the wrong key), that one pin will effectively block bolt 34 against longitudinal movement.

When the key 20 is fully inserted in the keyway slot 18 in the manner shown in FIG. 4, the front end of said key engages the lower portion of the plate 49 which overhangs the keyway slot 18 and presses the plate 49 rearwardly against tension of spring 45. The plate 49 slides along the reduced end portion 34a of bolt 34 until it is adjacent to or spaced slightly from the coupling disc 46, compressing spring 45 and removing its biasing tension from bolt 34. The bolt 34 is thus released to move rearwardly in its bore 56. However, even though all of the pins 28 are also elevated to their correct levels, in the manner previously explained to unlock the bolt 34, the latching mechanism will not be operated because the bolt end portion 34a is still out of engagement with the offset aperture 48 in the coupling disc 46. The bolt 34 would simply remain dormant in its inoperative position of FIG. 2, unless it were physically moved rearwardly into operative engagement with the latch mechanism 36. Separate means are therefore provided to slide the bolt 34 into coupling engagement with the latch mechanism 36, which means will now be described.

Mounted within a bottom recess 61 in cylinder 14, and offset from pins 28-, is a plug 64 in which is mounted the bottom end of an upstanding flat leaf spring 62, as shown in FIG. 2. The spring 62 extends upwardly through a recess in cylinder 14, and its free end extends into a cutaway portion 66 in the bottom of bolt 34. The groove 66 has a straight rear end forming a shoulder 68. The spring 62 is normally in the vertically-upstanding, untensioned position shown in FIG. 2, in which its free end is adjacent to the shoulder 68. Also mounted within cylinder 14 is a cam member 70 of the shape shown in FIGS. 7-9. The cam member 70 has an arcuate portion 72 and an integral arm portion 74 having a straight outer edge 74a and defining a notch Z6 therebetween. The arcuate portion 72 contains an arcuate slot 78 in which is received a pin 80 upstanding from plug 64. While the spring 62 is offset from the keyhole slot 18, the arm portion 74 of the cam member 70 extends a short distance within the slot 18, as shown in FIG. 9, and is adapted to be engaged and actuated by the inserted key 20, in a manner to be presently described, which actuation causes the spring 62 to be depressed and tensioued.

In the inoperative position of cam member 70, shown in FIG. 9*, the corner of cam member 70- projects within the keyway slot 18, and the cam member 70 rests upon plug '64 with pin 80 located at one end of the arcuate slot 78. In this position, an intermediate portion of the fiat spring 62 is located within the notch 76.

For purposes of actuating cam 70, the key 20 is provided with an elongated, laterally-projecting land 82 extending along one side thereof. This land 82 has a rectangular cut-away portion 84 intermediate its ends, as (best seen in FIGS. 3 and 9, which cut-away portion 84 is positioned to register with the cam 70 in the fullyinserted position of the key 20, as shown in FIGS. 4 and 9.

Operation of the lock will now be understood. When the key 20 is inserted into the keyhole 16 and slid through the keyway slot 18, the inclined tip of the key engages each of the rounded ends of the pins 28 in the usual manner, raising the pins and causing the rounded free ends thereof to ride along the top surface of the key as the latter continues to be inserted. At the same time, the land 82 at the side of the key 20' engages the straight edge 74a of cam arm 74, turning the cam 70 to a position in which the arm portion 74 is parallel to the land 82 and rides along the top surface of said land 82, as shown in FIG. 8. The cam 70 is turned in a clockwise direction, as viewed in FIG. 9, until the pin 80 is located at the opposite end of slot 78. The turning movement of cam 70 defined by the pin 80 and slot 78, moves the cam 70 to the actuating position of FIG. 8 in which the end of the arcuate portion 72 engages spring 62, depressing the latter and moving it forwardly away from the shoulder 68 at the end of groove 66. This depressed position of spring 62 is shown in FIG. 3, the spring being bent and primed for producing an actuating stroke.

It will be observed in FIGS. 3 and 4 that the slots and ridges on the upper surface of key 20 are made longer than is usual, so that shortly before the key 20 reaches its fully-inserted position, the slots and ridges on the upper surface of the key raises each of the pins 28 to the proper level so that the respective recessed portions 60 of all the pins 28 register with the bolt 34 and release the latter for sliding movement. Further movement of the key towards its fully-inserted position brings the tip of the key out of the end of the keyhole slot 18 so that the key tip moves the plate 49 rearwardly as described heretofore, and removes from bolt 34- the biasing force of spring 45. When the key reaches its fully inserted position of FIG. 4, the rectangular cut away portion 84 of land 82 moves into registry with cam 70, as shown in FIG. 9, permitting the cam 70 to turn in a. counter clockwise direction. This turning movement of cam 70 releases the tensioued spring '62, which snaps rearwardly, from its primed position. As the spring 62 snaps rearwardly, its free end portion strikes the shoulder 68 at the end of groove 66, and drives the released bolt 34 in a rearward direction, or to the right as viewed in FIG. 3. The reduced end 34a of bolt 34 thus enters the aperture 48 in the coupling disc 46, so that the cylinder 14 is coupled to the latch mechanism 36 through bolt 34. When the inserted key 20 is turned to rotate the cylinder 14, the coupling disc 46 and flat bar 38' are turned in unison, thereby opening the door latch towhich the free end of the bar 38, is connected.

Free movement of bolt 34 into coupling engagement with the latch mechanism 36 is made possible because of the release of the tension of return spring 45 upon bolt 34. This is accomplished by the key 20*, which, as it approaches its fully-inserted position, engages the plate 49 and moves it rearwardly, as previously described.

The bolt 34 will remain in operative engagement with the latch mechanism, through coupling disc 46, as long as the key 20 is fully inserted and is depressing return spring 45.

It will be observed that the front wall of casing 12 has an inwardly-projecting annular flange 86 which is interrupted only at the central bottom portion 88 which registers with the keyhole 16 of cylinder 14 in the position of the latter shown in FIG. 2. The key 20 also has a notch 90 in its lower surface which is sized to receive the flange 86. Thus, the key can be inserted and removed through the flange opening 88 only when the cylinder is in the position of FIG. 2, with the pins 28 in the vertical positions shown. At other times, the flange 86 is located in the key notch 90 and prevents the key from being withdrawn. Thus, after the lock is opened, as previously described, the key 20 must be revolved back to the position shown in FIG. 2 before it can be removed from the lock.

When the key 20 is withdrawn, the cylinder 14 is first turned to the position of FIG. 2, in which the pins 28 are vertically-disposed, and in which the latch mechanism 36 is turned to the locked position of the latch. As the key 20 is slid outwardly of the keyway slot 18, the rectangular recess 84 moves out of registry with cam 70' and the land 82 engages cam 70 and turns it in a counter-clockwise direction, the cam 70 turning about pin as a pivot. This turning movement continues until the arcuate portion 72 of cam 70 is aligned with the keyway slot 18 and rides along the land 82 of the withdrawn key. The spring 62 is slightly tensioued within notch 76. Simultaneously, the tip of key 20 moves away from plate 49, allowing the return spring 45 to exert biasing pressure upon the bolt 34 through said plate 49, so as to drive the bolt 34 to the left, as viewed in FIG. 4, until it, the plate 49, comes to rest against the end portion 14a of cylinder 14. The return movement of plate 49 carries the bolt 34 back to its inoperative position of FIGS. 2 and 5 in which it is clear of the latch mechanism 36 and in which its notches 58 are aligned with pins 26. This return movement of the bolt 34 is accomplished before the pins 28 return to their lowered positions of FIG. 2, that is while the pins are still resting upon the flats of the key bits. Thus the notches 58 on bolt 34 are brought into alignment with the respective pins 26, and thereafter further withdrawing movement of the key is permitted by free vertical movement of the pins 26. When the key 20 is fully withdrawn, springs 30 bring the pins 28 back to their lowered positions of FIG. 2.

By the time the land 82 on key 20 has moved out of engagement with cam 70 to release the latter, the bolt notches 58 have moved into alignment with pins 26 and the latter have been moved out of their release positions, so that the pins 26 have again locked the bolt 34 in its retracted position of FIGS. 2 and 5. When the cam 70 is released by the key land 82, the spring 62, which was slightly tensioned, is operative to return the cam 70 to the position shown in FIG. 9.

If the wrong key is inserted in the lock 10, even if the key is provided with the land 82 and cut-away portion 84, the lock will not be opened. In this event, the pins 28 are not all raised to the proper levels in which they release the bolt 34 for sliding movement, and the bolt remains locked. Consequently, when the cam- 70 is actuated by the land 82 to tension and release spring 62, the tensioned spring 62 is released to strike the shoulder 68 of groove 66, but the bolt will not move, and the actuating stroke is wasted.

It will be appreciated that the lock 10 is pick-proof because there are no parts which are under tension. Such tension would enable the proper positioning of the pins 28 to be felt because of frictional binding. Rather, two independent opening operations occur in rapid succession. The pins 28 must first be properly aligned by insertion of the proper key to release bolt 34 for sliding movement. At this time, the bolt 34 is inert in the sense that there is no force or tension upon it which would cause it to slide longitudinally, and therefore a person tampering with the lock would be unable to feel when the pins are properly aligned. The spring 62 is independently tensioned and is not released until the key is fully inserted in the lock. The actuating stroke imparted by the spring 62 is not effective to open the lock unless the bolt 34 has already been released by the elevation of the pins 28 to their proper levels. The actuating stroke provided by spring 62 is also temporary and instantaneous, the end of spring 62 sharply striking shoulder 68 on bolt 34 and then returning to its vertically-upstanding position without maintaining sustained driving pressure upon the "bolt or pins which might be sensed by a person attempting to pick the lock.

While a preferred embodiment of the invention has been shown and described herein, it is obvious that numerous omissions, changes and additions may be made in such embodiment without departing from the spirit and scope of the invention.

What is claimed is:

1. A pick-proof lock comprising a cylinder rotatably mounted in a housing, a bolt mounted in said cylinder for sliding movement between a locking position and an unlocking position, bolt-retaining means slidably mounted in said cylinder and associated with said bolt to normally obstruct movement of said bolt out of its locking position, said bolt retaining means being movable upon insertion of a proper key in said lock to a position in which it releases said bolt to a dormant, unbiased state in which said bolt is free to slide to its unlocking position, an actuating member for driving said released bolt, and tensioning means operable upon insertion of said proper key in said lock for tensioning said actuating member as said key is being inserted and releasing the tensioned actuating member when said key reaches its fully inserted position, said actuating member being positioned to strike said bolt upon release of the tensioned actuating member to 8 impart to said bolt an instantaneous impulse stroke in a direction to drive said bolt to said unlocking position.

2. A pick-proof lock according to claim 1 in which said cylinder has a keyway for receiving the inserted key, and in which said bolt retaining means comprises a plurality of tumbler pins slidably mounted in said cylinder and extending into said keyway slot for individual movement to selected bolt-releasing positions upon insertion of the proper key into said keyway slot, said bolt having a plurality of circumferential notches formed therein, each of said pins extending through a respective notch to retain said bolt against sliding movement and being free of lateral bias by said bolt each of said pins also having a recessed portion which registers with said bolt when said pin is brought to said bolt-releasing position.

3. A pick-proof lock according to claim 2 in which said bolt has an elongated groove terminating in a shoulder, and in which said actuating member comprises a flat spring mounted at one end in said cylinder and having an opposite free end extending into said groove, said spring being bent away from said bolt shoulder by said tensioning means and thereafter being released when said key is fully inserted in said keyway to strike said shoulder and impart said impulse stroke to said bolt.

4. A pick-proof lock according to claim 3 in which said tensioning means comprises a cam member turnably mounted in said cylinder and having a first portion normally extending into said keyway slot in the path of a key inserted into said lock, said cam member having a second portion positioned to engage and tension said flat spring when said first portion is engaged and moved by a key inserted into said keyway slot.

5. A pick-proof lock according to claim 4 in combination with a key having an elongated longitudinal land projecting laterally from one side thereof and a recess in said land, said land engaging said first portion of said cam member when said key is inserted into said keyway slot and said first portion riding along said land as said key is further inserted, said recess being positioned to register with said cam in the fully-inserted position of said key and being sized to provide clearance for said cam to turn in a direction to release said tensioned flat spring.

-6. A pick proof lock according to claim 1 in which said bolt is mounted offset from the central rotational axis of said cylinder whereby said bolt revolves about said axis when said cylinder is rotated, and in which latch operating means is rotatably mounted in the rear wall of said housing and remote from said bolt when the latter is in its locking position, said bolt sliding into gripping engagement wth said latch operating means in response to receiving said actuating stroke by said actuating member, whereby said bolt couples said actuating means to said cylinder for simultaneous rotation thereof.

7. A pick proof lock according to claim 6 in which a plate is slidably mounted between said cylinder and the rear wall of said casing, said plate engaging said bolt, and spring means biasing said plate away from said rear wall and in a direction to urge said bolt toward its locking position.

8. A pick proof lock according to claim 7 in which said plate has a portion overlying said keyway and positioned to be engaged by the inserted key and moved thereby toward said rear Wall to a position in which said plate compresses said spring means and removes the biasing tension thereof from said bolt.

9. A pick-proof lock comprising a keyway for receiving a key capable of opening said lock when inserted in said keyway to a fully-inserted position, a bolt slidably mounted within said lock for movement between a locking position and a lock-release position, bolt retaining means movably mounted within the interior of said lock and normally urged to an active position in which it engages said bolt and holds the latter rigidly in said looking position against sliding movement, said bolt retaining means having a portion located in said keyway and re- 10 sponsive to engagement by said key inserted in said key- References Cited way for moving said bolt retaining means to an inactive position in Which it disengages from said bolt, said bolt, UNITED STAFJTES PATENTS upon disengagement from said bolt retaining means being 1,455,577 5/ 1923 Epstein 70419 in a dormant, unbiased state in which it is free to slide 5 23873175 6/1942 Heyer 70364 to its lock-release position, and spring means responsive 2,295,737 9/ 1942 Johnstone 70-364 to insertion of said key in said keyway, for imparting an 3,455,130 7/1969 Basseches 70*421 instantaneous impulse stroke to said bolt in a direction to drive said bolt to said lock-release position, said spring ROBERT WOLFE Pnmary Exammer means being positioned to impart said impulse stroke to 10 U S Cl X R said bolt only after said key reaches its fully-inserted position. 379, 419 

